Cellular phones have evolved from large devices that were only capable of analog voice communications to comparatively smaller devices that are capable of digital voice communications and digital data communications, such as Short Message Service (SMS) for text messaging, email, packet switching for access to the Internet, gaming, Bluetooth, and Multimedia Messaging Service (MMS) to provide some examples. In addition to these capabilities, the cellular phones of today have additional non-communication related capabilities, such as a camera with video recording, an MPEG-1 Audio Layer 3 (MP3) player, and software applications such as a calendar and a phone book, to provide some examples. Even in light of these capabilities, manufacturers of cellular phones are placing even more capabilities into cellular phones and making these more power cellular phones smaller.
At the heart of each cellular phone lies a power management unit (PMU). The PMU is responsible for monitoring power connections and battery charges, charging batteries when necessary, and controlling power to other integrated circuits, as well other power functions of the cellular phone. The PMU may include a battery charger to charge or restore one or more batteries for the operation of the cellular phone. Conventionally, the battery charger includes a sensing resistor to measure the output current provided to the battery to ensure proper restoration of the battery. This sensing resistor, however, dissipates power, in the form of heat to provide an example, which could be otherwise used to restore the battery, thereby reducing an efficiency of the battery charger. Additionally, the battery charger may be implemented using one or more dies or chips, but because of their size, the sensing resistor is often implemented external to these dies or chips, thereby increasing the overall size of the battery charger.
Thus, there is a need for a battery charger to measure the output current provided to the battery to ensure proper restoration of the battery without the use of the sensing resistor that overcomes the shortcomings described above. Further aspects and advantages of the present invention will become apparent from the detailed description that follows.
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the reference number.